<My first calculator, a Sinclair Cambridge, did that as well. Perhaps
<someone on the list could enlighten us as to whehter this was a common
<weakness of early calculators, and possibly why those who wrote the code
<them allowed it to happen ;-)
many of them were hard logic and not "programmed micros". Logic errors
are the responseable element and it was common for the same(literal)
chip to appear in different branded calculators.
later designs did however use the likes of the TMS1000, a 4bit data
oriented, 8bit instruction word masked rom single chip micro. NEC, MOTO
and a few others had parts in that market as they could be made cheap in
volume with their masked roms.
Allison